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            <h2 class="title"><a id="addfeatures"></a>Chapter 5. Additional Features</h2>
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            <span class="sect1">
              <a href="addfeatures.html#delayedsync">Delayed Synchronization</a>
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              <a href="rywc.html">Read-Your-Writes Consistency</a>
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              <a href="c2ctransfer.html">Client to Client Transfer</a>
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                <span class="sect2">
                  <a href="c2ctransfer.html#fmwrkpeerserver">Identifying Peers</a>
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      <p>
            Beyond the basic functionality that we have discussed so far in
            this book, there are several replication features that you
            should understand. These are all optional to use, but provide
            useful functionality under the right circumstances.
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            These additional features are:
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                            <a class="xref" href="addfeatures.html#delayedsync" title="Delayed Synchronization">Delayed Synchronization</a>
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                            <a class="xref" href="manageblock.html" title="Managing Blocking Operations">Managing Blocking Operations</a>
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              <h2 class="title" style="clear: both"><a id="delayedsync"></a>Delayed Synchronization</h2>
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        <p>
                When a replication group has a new master, all replicas must
                synchronize with that master. This means they must ensure
                that the contents of their local database(s) are identical
                to that contained by the new master.
        </p>
        <p>
                This synchronization process can result in quite a lot of
                network activity. It can also put a large strain on the
                master server, especially if is part of a large
                replication group or if there is somehow a large difference between
                the master's database(s) and the contents of its replicas. 
        </p>
        <p>
                It is therefore possible to delay synchronization for any
                replica that discovers it has a new master. You would do
                this so as to give the master time to synchronize other
                replicas before proceeding with the delayed replicas.
        </p>
        <p>
                To delay synchronization of a replica environment, you
                specify 
                    <span>
                        <code class="literal">DB_REP_CONF_DELAYCLIENT</code> to
                            <code class="methodname">DB_ENV-&gt;rep_set_config()</code>
                            
                        and then specify <code class="literal">1</code> to the <code class="literal">onoff</code>
                        parameter. (Specify <code class="literal">0</code> to turn the feature off.)
                    </span>
                    
        </p>
        <p>
                If you use delayed synchronization, then you must manually
                synchronize the replica at some future time. Until you do this, the replica is out of
                sync with the master, and it will ignore all database changes forwarded to it from 
                the master. 
        </p>
        <p>
                You synchronize a delayed replica by calling
                    <code class="methodname">DB_ENV-&gt;rep_sync()</code>
                    
                    
                on the replica that has been delayed.
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